Dynamic damper and flywheel assembly

ABSTRACT

A dynamic damper 70 is employed in a coupling mechanism 91 for coupling a crankshaft 90 of an engine and an input shaft 9 of a transmission. The dynamic damper 70 is designed to reduce a force applied in the rotating direction to components of a sub-clutch. Thus, the dynamic damper 70 reduces the cost and the size of the sub-clutch of the dynamic damper. The dynamic damper 70 is adapted to be coupled to the input shaft 9 to rotate therewith. The dynamic damper 70 basically includes a mass member 71, a sub-clutch 73 and an annular rubber member 72. The mass member 71 can rotate in accordance with rotation of the input shaft 9. The sub-clutch 73 reduces a torque transmitted between the input shaft 9 and the mass member 71 when a main clutch 3 disengages the crankshaft 90 and the input shaft 9 from each other. The annular rubber member 72 elastically couples the input shaft 9 and the mass member 71 in the rotating direction when they are in the interlocked state.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to a dynamic damper and a flywheelassembly. More specifically, the present invention relates to a dynamicdamper which operates in accordance with an operation of an input shaftof a transmission for dampening a vibration.

2. Background Information

In connection with such a dynamic damper and a flywheel assembly, theassignee has already developed prior arts disclosed in JapaneseLaid-Open Patent Publication No. 6-48031 (1994) and others.

In the above prior arts, a second flywheel forming a mass portion iscoupled to a drive and transmission system through a torsional dampermechanism to dampen a torsional vibration on the drive and transmissionsystem only when a clutch disk is pressed against a first flywheel.Thereby, an operation impeding shifting of the transmission issuppressed in a disengaged state of a clutch while suppressing gearnoises (neutral noises) of the transmission in a neutral state as wellas vibrations and noises of the transmission during driving of avehicle.

In the above prior art, a frictional dampening mechanism (sub-clutch) isused for disengageably coupling the second flywheel to the transmissionand drive system. When an operation is performed to couple the secondflywheel to the drive and transmission system, a large difference ispresent between rotation speeds of the second flywheel and the drive andtransmission system so that a large load is applied to a portion of thefrictional dampening mechanism. Therefore, components of the frictionaldampening mechanism must have a sufficient strength, which increases acost and a size of the frictional dampening mechanism.

In view of the above, there exists a need for dynamic dampers andflywheel assemblies which reduce the forces applied to the components ofthe sub-clutch to reduce the size and costs of the sub-clutch. Thisinvention addresses this need in the prior art as well as other needs,which will become apparent to those skilled in the art from thisdisclosure.

SUMMARY OF THE INVENTION

An object of the present invention is to reduce a force in the rotatingdirection, which is applied to the components of the sub-clutch duringthe operation of engaging the sub-clutch, and thereby reduce a cost anda size of the sub-clutch of the dynamic damper.

According to a first aspect of the present invention, a dynamic damperis operable in a coupling mechanism to perform an operation interlockedwith an input shaft of a transmission and includes a mass portion, asub-clutch and an elastic portion. The coupling mechanism is providedfor coupling a crankshaft of an engine and the input shaft of thetransmission, and includes a main clutch. The mass portion is operablein accordance with rotation of the input shaft of the transmission. Thesub-clutch reduces a torque transmitted between the input shaft of thetransmission and the mass portion when the main clutch releases thecoupling between the crankshaft of the engine and the input shaft of thetransmission. The elastic portion elastically couples the input shaft ofthe transmission and the mass portion in the rotating direction when theinput shaft of the transmission and the mass portion are interlockedtogether by the sub-clutch.

In this coupling mechanism provided with the dynamic damper, a torquesupplied from the crankshaft of the engine is transmitted to the inputshaft of the transmission through the main clutch.

When the main clutch is in the engaged state, the sub-clutch attains theinterlocked state in which the dynamic damper operates in accordancewith the rotation of the input shaft of the transmission. Therefore, thedynamic damper dampens noises during the neutral state of thetransmission and noises during driving. The above structure does notemploy an inertia damper, which avoids a resonance by mere addition ofan inertia, but employs the dynamic damper. Therefore, it is possible todampen the vibration of the input shaft of the transmission in a partialrotation range. Consequently, the vibration can be reduced to a level,which cannot be attained by the internal damper.

When the main clutch is in the disengaged state, the sub-clutchtransmits a torque, which is smaller than that transmitted between theinput shaft of the transmission and the mass portion during the engagedstate of the main clutch, from the input shaft of the transmission tothe mass portion. Thus, the sub-clutch is not completely disengaged evenwhen the main clutch is in the disengaged state, and the mass portion ofthe dynamic damper rotates at a speed close to the rotation speed of theinput shaft of the transmission. When the operation is being performedto engage the main clutch, a difference between the rotation speeds ofthe mass portion and the input shaft of the transmission can thereforebe small so that a force applied to components of the sub-clutch can besmall. Accordingly, it is necessary to reduce a required strength of thecomponents of the sub-clutch, and the cost and size of the sub-clutchcan be reduced.

However, it is desired to reduce an inertia of the input shaft of thetransmission for smoothening the shifting operation of the transmissionwhich is performed when disengaging the main clutch. Therefore, it isrequired to reduce a torque, which is transmitted between the dynamicdamper and the input shaft of the transmission while the main clutch isdisengaged. The above requirement runs counter to the mechanism in whichthe sub-clutch is not completely disengaged even when the main clutch isdisengaged. Therefore, both of these requirement and fact are taken intoconsideration when determining and setting the torque, which istransmitted by the sub-clutch between the input shaft of thetransmission and the mass portion when the main clutch is disengaged.

According to a second aspect of the present invention, the dynamicdamper according to the first aspect of the present invention furtherhas such a feature that the sub-clutch is a frictional engagementclutch. In this aspect of the present invention, a difference betweenthe rotation speeds of the mass portion and the input shaft of thetransmission is small when engaging the main clutch. Therefore, a forceacting in the rotating direction on frictional members forming thesub-clutch can be small. Therefore, wearing of the friction members ofthe sub-clutch is suppressed, and the sub-clutch can have an increasedlifetime.

According to a third aspect of the present invention, the dynamic damperaccording to the first aspect of the present invention further has sucha feature that the sub-clutch is a gear meshing type clutch. In thisaspect of the present invention, a difference between the rotationspeeds of the mass portion and the input shaft of the transmission issmall when engaging the main clutch. Therefore, a force acting in therotating direction on gear members forming the sub-clutch can be small.Therefore, damage to the gear members of the sub-clutch is suppressed,and the sub-clutch can have an increased lifetime.

According to a fourth aspect of the present invention, a flywheelassembly includes a flywheel and a dynamic damper. The flywheel isnon-rotatably coupled to a crankshaft of an engine. The flywheel isdisengageably coupled to a clutch disk assembly coupled to an inputshaft of a transmission. The dynamic damper is the same as thataccording to any one of the preceding first to third aspects of thepresent invention. In this aspect of the present invention, the dynamicdamper is incorporated together with the flywheel in the flywheelassembly. This facilitates an assembly operation for attaching theflywheel assembly to the crankshaft of the engine, the clutch diskassembly or the input shaft of the transmission.

According to a fifth aspect of the present invention, the flywheelassembly according to the fourth aspect further includes a plate member.The plate member has an inner peripheral portion fixed to the crankshaftof the engine, and an outer peripheral portion fixed to the flywheel.The plate member has a predetermined rigidity and absorbs a vibrationalong a rotation axis. In this aspect of the present invention, theplate member is interposed between the crankshaft of the engine and theflywheel. Therefore, it is also possible to reduce the axial vibrationby the flywheel assembly.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which, taken in conjunction with theannexed drawings, discloses preferred embodiments of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a partial cross-sectional view of the upper half of a flywheelassembly with a dynamic damper in accordance with one embodiment of thepresent invention;

FIG. 2 is a partial inside elevational view of the mass member of theflywheel assembly illustrated in FIG. 1;

FIG. 3 is an enlarged partial cross-sectional view of an elastic portionassembly of the flywheel assembly illustrated in FIG. 1;

FIG. 4 is a right side elevational view of the elastic portion assemblyillustrated in FIGS. 1 and 3 as viewed from the engine side of theflywheel assembly illustrated in FIG. 1;

FIG. 5 is a left side elevational view of the elastic portion assemblyillustrated in FIGS. 1, 3 and 4 as viewed from the transmission side ofthe flywheel assembly illustrated in FIG. 1;

FIG. 6 is an enlarged partial cross-sectional view of part of thesub-clutch and the position correcting mechanism of the flywheelassembly illustrated in FIG. 1;

FIG. 7 is an exploded cross-sectional view of selected parts of theflywheel assembly illustrated in FIG. 1;

FIG. 8 is a partial cross-sectional view of the sub-clutch of theflywheel assembly illustrated in FIGS. 1 and 7, with the sub-clutch in afirst disengaged position;

FIG. 9 is a partial cross-sectional view of the sub-clutch of theflywheel assembly illustrated in FIGS. 1 and 7, with the sub-clutch in asecond disengaged position;

FIG. 10 is a partial cross-sectional view of the sub-clutch of theflywheel assembly illustrated in FIGS. 1 and 7, with the sub-clutch in afirst engaged position;

FIG. 11 is a partial cross-sectional view of the sub-clutch of theflywheel assembly illustrated in FIGS. 1 and 7, with the sub-clutch in asecond engaged position;

FIG. 12 is a side elevational view, similar to FIG. 4, of the elasticportion assembly but with it in a deformed state;

FIG. 13 is a partial cross-sectional view of a flywheel assembly with adynamic damper employed in a coupling mechanism in accordance with asecond embodiment of the present invention;

FIG. 14 is a partial cross-sectional view of the sub-clutch of theflywheel assembly illustrated in FIG. 13 in accordance with the secondembodiment of the present invention;

FIG. 15 is a left side elevational view of the flywheel illustrated inFIG. 13; and

FIG. 16 is a left side elevational view of the three release members,arranged in a circular pattern, for use in the flywheel assemblyillustrated in FIGS. 13 and 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIGS. 13 and 14, a partial cross-sectional viewof a coupling mechanism 91 is illustrated in accordance with oneembodiment of the present invention. The coupling mechanism 91 isbasically formed of a flywheel assembly 60 and a main clutch 3 formed ofa clutch cover assembly 4 and a clutch disk assembly 5. The couplingmechanism 91 has a rotation axis represented by line O--O of FIG. 13.

The flywheel assembly 60, which is illustrated in FIG. 13, includes adynamic damper 70 in accordance with one embodiment of the presentinvention. The flywheel assembly 60 and the dynamic damper 70 are partof a coupling mechanism 91, which engages and disengages a crankshaft 90of an engine with an input shaft 9 of a transmission. The dynamic damper70 functions to damp vibrations of the transmission when coupled to theinput shaft 9 of the transmission by a sub-clutch 73.

The flywheel assembly 60 is non-rotatably coupled to the crankshaft 90of the engine, and is basically formed of a flywheel 61, a housingmember 62 and the dynamic damper 70. The flywheel 61 and the housingmember 62 are coupled together at their outer peripheries. The flywheel61 is provided with a plurality of recesses or concavities 61b which arelocated on a transmission side (right side in FIG. 13) of its outerperipheral portion. The flywheel 61 is also provided with a plurality ofholes 61a which extend axially through the flywheel 61 from centers ofbottom surfaces of the concavities 61b (i.e., surfaces defining the leftends of the concavities near the engine), respectively. The radiallyinner portion of the housing member 62 is fixed to the crankshaft 90 ofthe engine by circumferentially equally spaced bolts. The dynamic damper70 will be described later in more detail.

The clutch cover assembly 4 of the main clutch 3 is basically formed ofa clutch cover 4a, an annular diaphragm spring 4b and a pressure plate4c. The clutch cover assembly 4 of the main clutch 3 is normally biasedtoward the engine (i.e., to the left as viewed in FIG. 13) by thediaphragm spring 4b. The clutch cover 4a is fixed at its outerperipheral portion to an end of the flywheel 61 near the transmission(i.e., right end as viewed in FIG. 13). The inner peripheral portion ofthe clutch cover 4a carries a radially middle portion of the diaphragmspring 4b via wire rings 4d in a conventional manner. The pressure plate4c is held within the clutch cover 4a by the outer peripheral portion ofthe diaphragm spring 4b as well as by conventional parts, which are wellknown in the art. When a release bearing (not shown) moves the innerperiphery of the diaphragm spring 4b along the rotation axis O--O, thepressure plate 4c moves axially for biasing the pressure plate 4c by thediaphragm spring 4b and/or releasing the diaphragm spring 4b from thesame. The clutch cover assembly 4 operates to bias the pressure plate 4ctoward the flywheel 61, and thereby operates to hold the clutch diskassembly 5 between the flywheel 61 and the pressure plate 4c forfrictionally engaging the flywheel assembly 4 and the clutch diskassembly 5 together.

The clutch disk assembly 5 of the main clutch 3 is basically formed of africtional engagement portion having friction facings 5a, a splined hub5c and coil springs (not shown). The splined hub 5c has a splined innerbore that engages the splines of the input shaft 9 of the transmission.The coil springs (not shown) elastically couple the frictionalengagement portion and the spline hub 5c together in the rotatingdirection.

Referring now to FIG. 14, the structure of the dynamic damper 70 willnow be described below in more detail. The dynamic damper 70 isbasically formed of an annular mass member (mass portion) 71, an annularrubber member 72, an input portion formed of a circular support plate 74and a sub-clutch housing 81, the sub-clutch 73 and a circular plate 75.

The input portion of the dynamic damper 70 is formed of the circular orannular support plate 74 and the sub-clutch housing 81, which are fixedtogether by rivets as shown in FIG. 13. The annular rubber member 72elastically couples the mass member 71 to the input portion incircumferential, axial and radial directions. The sub-clutch housing 81is formed of a circular plate portion 81a, a fixing portion 81b, acylindrical portion 81c, and an axial restriction portion 81d. Thefixing portion 81b extends axially from the inner periphery of thecircular portion 81a toward the transmission and then further extendsradially inward toward the axis O--O. The cylindrical portion 81cextends axially from the outer periphery of the circular plate portion81a toward the transmission. The axial restriction portion 81d extendsradially inward from the end of the cylindrical portion 81a near thetransmission. The cylindrical portion 81c is provided with a pluralityof circumferentially spaced openings.

The inner peripheral portion of the input portion of the dynamic damper70 is fixedly coupled to an outer race 7a of a ball bearing 7.Specifically, the inner peripheral portion of the circular support plate74 and the fixing portion 81b of the sub-clutch housing 81 secure theinput portion to an outer race 7a of a ball bearing 7. An inner race 7bof the ball bearing 7 is fixedly coupled to the crankshaft 90 of theengine so that the input portion is supported rotatably on thecrankshaft 90 of the engine but unmovably on the crankshaft 90 of theengine in the axial and radial directions.

The input portion is adhered at its outer peripheral portion to theinner peripheral surface of the annular rubber member 72. Morespecifically, the inner peripheral surface of the annular rubber member72 is fixedly coupled to the outer peripheral portion of the circularsupport plate 74 and the outer peripheral surface of the cylindricalportion 81c of the sub-clutch housing 81.

The sub-clutch 73 is a clutch mechanism of a frictional engagement typefor engaging and disengaging the foregoing three components, i.e., themass member 71, annular rubber member 72 and input portion with and fromthe input shaft 9 of the transmission. The sub-clutch 73 is of africtional engagement type. The sub-clutch 73 is basically formed of thesub-clutch housing 81, a friction plate 82, a coupling member 84, aconical spring 85, one or more release members 86 with seats 87 attachedthereto and one or more coil springs 88.

The friction plate 82 is formed of an outer peripheral portion 82a witha pair of annular friction members 83 located on its axially oppositesurfaces, respectively, an inner peripheral portion 82b and a pluralityof claws 82c. The inner peripheral portion 82b extends radially inwardand obliquely from the inner periphery of the outer peripheral portion82a toward the transmission. The claws 82c project radially inward fromthe inner periphery of the inner peripheral portion 82b.

The coupling member 84 is formed of a radially inner circular plateportion 84, a plurality of intermediate levers 84b and radially outerlever portions 84c. The intermediate levers 84b extend radially outwardand obliquely from the radially inner circular plate portion 84a towardthe transmission. The radially outer lever portions 84c extend radiallyoutward from the radially outer ends of the intermediate levers 84b,respectively. The radially inner circular plate portion 84a has radiallyinner portions, which extend through openings formed at the cylindricalportion 81c, and therefore is axially movable.

The conical spring 85 has an outer periphery, of which movement towardthe transmission is restricted by the axial restriction portion 81d ofthe sub-clutch housing 81. The conical spring 85 has an inner peripherywhich biases the outer peripheral portion 82a of the friction plate 82toward the input portion (i.e., circular plate portion 81a of thesub-clutch housing 81) via the radially inner circular plate portion 84aof the coupling member 84.

As shown in FIGS. 13 and 16, the release members 86 are each formed of aconnecting portion 86a and an engagement portion 86b extending radiallyinward from the end of the connecting portion 86a near the engine. Whilethree release members 86 are illustrated, it will be apparent to thoseskilled in the art that the number of release members is a matter ofdesign choice. Thus, fewer or more release members can be used as neededand/or desired. The release members 86 extend through the holes 61a inthe flywheel 61 as seen in FIG. 13. The release members 86 aresubstantially L-shaped members or hooks, which are circumferentiallyspaced apart from each other as seen in FIG. 16. The ends of the postsforming the connecting portions 86a near the transmission are fixedlycoupled to the circular seats 87 by caulking or other means forpreventing separation from the same. The surfaces of the engagementportions 86b opposed to the transmission contact the lever outerperipheral portion 84c of the coupling member 84. More specifically, theengagement portions 86b are in contact with the surface of the leverouter peripheral portion 84c, which is opposed to the engine.

Each coil spring 88 is arranged within one of the concavities 61b in theflywheel 61 for continuously pressing the circular seats 87 against thepressure plate 4c. Thereby, the circular seats 87 and the releasemembers 86 follow the axial movement of the pressure plate 4c.

The circular plate 75 couples the input shaft 9 of the transmission andthe friction plate 82 of the sub-clutch 73. The inner periphery of thecircular plate 75 is fixed to the spline hub 5c, which in turn is fixedto the input shaft 9. The circular plate 75 has a plurality of claws75a, which extend from the outer periphery thereof toward the engine(i.e., to the left as viewed in FIG. 13). The claws 75a arecircumferentially engaged with claws 82c of the friction plate 82.Therefore, the friction plate 82 is non-rotatably coupled to thecircular plate 75, but is axially movable with respect to the circularplate 75.

The operation of the coupling mechanism 91 and the dynamic damper 70will now be described in more detail. The rotation of the crankshaft 90of the engine is transmitted to the input shaft 9 of the transmissionthrough the flywheel assembly 60 and the main clutch 3. When the mainclutch 3 is in the engaged state shown in FIG. 13, the pressure plate 4cis biased toward the flywheel 61 by a biasing force of the diaphragmspring 4b so that the clutch disk assembly 5 is held between theflywheel 61 and the pressure plate 4c. Thereby, the crankshaft 90 of theengine is coupled to the input shaft 9 of the transmission. In thisstate, as shown in FIG. 13, the friction plate 82 is biased by theconical spring 85 toward the engine so that the sub-clutch housing 81and the friction plate 82 are frictionally engaged. Therefore, the inputshaft 9 of the transmission is coupled to the mass member 71 of thedynamic damper 70, annular rubber member 72 and input portion throughthe circular plate 75 and the friction plate 82.

When the dynamic damper 70 is coupled to the input shaft 9 of thetransmission, the dynamic damper 70 damps neutral noises during theneutral state of the transmission and noises during driving.Particularly, the vibrations of the transmission are actively dampenedby the dynamic damper 70 in a partial rotational range.

When the main clutch 3 is released and the pressure plate 4c movestoward the transmission, the release members 86 move toward thetransmission together with the pressure plate 4c. Thereby, the couplingmember 84 moves toward the transmission against the elastic force of theconical spring 85 to decrease the torque transmission capacity achievedby the frictional engagement between the friction plate 82 and thesub-clutch housing 81. Thus, even when the main clutch 3 is in thedisengaged state, the sub-clutch 73 is disengaged only incompletely sothat the mass member 71, annular rubber member 72 and the input portionof the dynamic damper 70 rotate at a speed close to the rotation speedof the input shaft 9 of the transmission.

The advantages which can be achieved by employment of the structure ofthis embodiment will now be described in more detail. First, the massmember 71 is radially and axially carried at its radially inner side.Thus, the mass member 71 is coupled to the input portion connected tothe input shaft 9 of the transmission by the annular rubber member 72.This arrangement results in a structure that the annular rubber member72 concentratedly functions to hold and position the input portion ofthe mass member 71 in the circumferential, radial and axial directions.Therefore, it is not necessary to arrange an independent supportmechanism or the like, for example, radially outside the mass member 71,which allows increase in mass of the mass member 71 and therefore it ispossible to increase a range in which damper characteristics can be set.The annular rubber member 72 may have an anisotropy, which allowssatisfactory setting of elastic characteristics of the annular rubbermember 72 in the rotating direction corresponding to the dampercharacteristics and satisfactory of the elastic characteristics of theannular rubber member 72 in the radial direction for supporting the massmember 71 without interfering with another member.

Secondly, the dynamic damper 70 employs the annular rubber member 72.This results in the annular rubber member 72 having an elasticity notonly in the rotating direction but also in the axial direction.Therefore, the annular rubber member 72 operates as the dynamic damperwith respect to the axial vibrations for damping the axial vibration.

Thirdly, even when the main clutch 3 is in the disengaged state, thesub-clutch 73 is not completely disengaged. In particular, the dynamicdamper 70 rotates at a speed close to the rotation speed of the inputshaft 9 of the transmission. This reduces a difference which occurs inrotation speed between the dynamic damper 70 and the input shaft 9 ofthe transmission during the engaging operation of the main clutch 3.Therefore, a rotational force acting on the friction members 83 of thefriction plate 82 also decreases. Accordingly, conditions for selectingthe material of the friction member 83 is relaxed so that the cost ofthe friction member 83 can be lower than in the prior art.

However, it is desired to reduce an inertia of the input shaft 9 of thetransmission for smoothening the shifting operation of the transmissionwhich is performed together with the disengaging operation of the mainclutch 3. Therefore, it is required to reduce a torque, which istransmitted between the input portion of the dynamic damper 10 and theinput shaft 9 of the transmission while the main clutch 3 is disengaged.The above requirement runs counter to the mechanism in which thesub-clutch 73 is not completely disengaged even when the main clutch 3is disengaged. Therefore, requirements are taken into consideration whendetermining and setting the torque which is transmitted by thesub-clutch 73 between the input shaft 9 of the transmission and theinput portion of the dynamic damper 10 when the main clutch 3 isdisengaged.

Fourthly, the coupling mechanism 91 employs the release members 86,which moves together with a movement of the pressure plate 4c, forreleasing the operation of the sub-clutch 73 in the interlocked manner.The axial distance of movement of the pressure plate 4c is larger thanthe distance of movement of the clutch disk assembly 5. Therefore,engaging and disengaging of the sub-clutch 73 can be performed stablycompared with the structure in which the sub-clutch is operated byutilizing the axial movement of the clutch disk assembly 5.

The dynamic damper 70 according to the present invention employs theelastic portion including the rubber member which has elasticities inthe rotating and axial directions, and can dampen not only the torsionalvibrations but also the axial vibrations.

According to the present invention, before the cavity disappears, theelastic portion expands and contracts in the rotating direction owing tothe elasticity of the rubber members. In particular, before the cavitydisappears, the elasticity of the elastic portion, which is primarilyresponsible for controlling vibrations, is the portions of the rubbermembers other than the portions on the transmission input shaft side andthe mass portion side. After the cavity disappears, the elastic portionexpands and contracts in the rotating direction owing to the elasticityof the portions of the rubber members on the transmission input shaftside and the mass portion side. Therefore, the rubber members canreliably have an intended strength in spite of the fact that the rubbermembers are employed in the dynamic damper. Also, the dynamic damper canhave several kinds of dampening characteristics only by employing asimple manner, i.e., provision of the cavity in the rubber members.

Second Embodiment

Referring now to FIG. 1, a partial cross-sectional view of a couplingmechanism 1 is illustrated in accordance with one embodiment of thepresent invention. The coupling mechanism 1 is basically formed of aflywheel assembly 2 and a main clutch 3. The main clutch 3 includes aclutch cover assembly 4 and a clutch disk assembly 5. The couplingmechanism 1 has a rotation axis represented by line O--O of FIG. 1.

The flywheel assembly 2, which is illustrated in FIG. 1, includes adynamic damper 10 in accordance with one embodiment of the presentinvention. The flywheel assembly 2 and the dynamic damper 10 are part ofa coupling mechanism 1, which engages and disengages a crankshaft 8 ofan engine with an input shaft 9 of a transmission. The dynamic damper 10functions to dampen vibrations of the transmission when coupled to theinput shaft 9 of the transmission by a sub-clutch 13.

The flywheel assembly 2 is non-rotatably coupled to the crankshaft 8 ofthe engine. The flywheel assembly 2 is basically formed of a flywheel2a, a flexible plate assembly 2b and the dynamic damper 10. As shown inFIG. 7, the flywheel assembly 2 is illustrated in an exploded form toshow selected parts of the flywheel assembly 2. The flywheel 2 and theflexible plate assembly 2b are coupled together at their outerperipheral portions as shown in FIG. 1 in a conventional manner. Theflexible plate assembly 2b is basically formed of a thick circular platehaving a thin flexible plate 2c fixed to the inner peripheral portion ofthe thick circular plate. In particular, the inner end of the thinflexible plate 2c is fixedly secured to the inner end of the thickcircular plate. The other end of the flexible plate 2c is fixed to thecrankshaft 8 of the engine by seven bolts 8a, which arecircumferentially and equally spaced from each other. The dynamic damper10 will be described later in detail.

As shown in FIG. 1, the clutch cover assembly 4 of the main clutch 3basically includes a clutch cover 4a, an annular diaphragm spring 4b anda pressure plate 4c. The clutch cover assembly 4 of the main clutch 3 isnormally biased toward the engine (i.e., leftward as viewed in FIG. 1)by the diaphragm spring 4b. The clutch cover 4a is fixed at its outerperipheral portion to an end of the flywheel 2a near the transmission(i.e., right end as viewed in FIG. 1). The inner peripheral portion ofthe clutch cover 4a carries a radially middle portion of the diaphragmspring 4b via wire rings (not shown) in a conventional manner. Thepressure plate 4c is held within the clutch cover 4a in a conventionalmanner by the outer peripheral portion of the diaphragm spring 4b andother parts (not shown). The pressure plate 4c axially moves when arelease bearing (not shown) moves the inner periphery of the diaphragmspring 4b along the rotation axis O--O, i.e., in the axial direction forbiasing the pressure plate 4c by the diaphragm spring 4b or releasingthe diaphragm spring 4b from the same. The clutch cover assembly 4operates to bias the pressure plate 4c toward the flywheel 2a, andthereby operates to hold the clutch disk assembly 5 between the flywheel2a and the pressure plate 4c for frictionally engaging the flywheelassembly 4 and the clutch disk assembly 5 together.

The clutch disk assembly 5 of the main clutch 3 is basically formed of africtional engagement portion with friction facings 5a, a splined hub 5cand coil springs 5b. The splined hub 5c has an inner bore with splinesfor engaging the splines of the input shaft 9 of the transmission forrotation therewith. The coil springs 5b elastically couple thefrictional engagement portion and the splined hub 5c together in therotating direction.

Referring to FIGS. 1 and 7, a structure of the dynamic damper 10 will bedescribed below. The dynamic damper 10 is basically formed of a massmember (mass portion) 11, elastic portion assemblies (elastic portions)12, an input plate (input portion) 14 and a sub-clutch 13.

The mass portion 11 has an annular mass main portion 11a and annular orcircular plate portion 11b. The main portion 11a has a generallytriangular cross section which diverges radially outward. The annular orcircular plate portion 11b is integrally formed at the inner section ofthe main portion 1a, as shown in FIGS. 1 and 2. The circular plateportion 11b is preferably provided with ten circular apertures 11c whichare circumferentially equally spaced from each other, as shown in FIG.2. Each of the circular apertures 11c receives one of the elasticportion assemblies 12 therein.

The elastic portion assemblies 12 elastically couple the mass portion 11and the input plate 14 together, as shown in FIGS. 1 and 3. As shown inFIGS. 3 to 5, each elastic portion assembly 12 is formed of acylindrical rubber member 21, a radially outer cylindrical member 22,and a radially inner cylindrical member 23. The outer cylindrical member22 is fixed to the outer peripheral surface of the rubber member 21. Theradially inner cylindrical member 23 is fixed to the inner peripheralsurface of the rubber member 21. The radially outer and innercylindrical members 22 and 23 are made of a hard rigid material such assteel.

Each of the rubber members 21 is integrally formed of a main portion(first rubber portion) 21a and an outer peripheral projection (secondrubber portion) 21b. The outer peripheral projection 21b is located onthe outer peripheral surface (upper surface) of the main portion 21a.More specifically, the outer peripheral projection 21b is located on theright side as viewed in FIG. 3 (i.e., the side near the transmission) ofthe main portion 21a. As shown in FIGS. 4 and 5, each rubber member 21is provided with two cavities 21c which extend axially therethrough. InFIGS. 4 and 5, directions R1 and R2 represent the circumferentialdirection, and a direction D1 represents a radial direction. As shown inFIG. 4, each cavity 21c has an oblong form or kidney-shaped with itslength extending in the radial direction and has its width (which willbe referred to as a space) S extending in the circumferential direction.Accordingly, cavities 21c are longer in the radial direction than in thecircumferential direction. Accordingly, cavities 21c are longer in theradial direction than in the circumferential direction.

The radially inner cylindrical member 23 has a cylindrical form and hasan axial length substantially equal to the axial length of the rubbermember 21 as shown in FIG. 3. The radially outer cylindrical member 22also has a substantially cylindrical form. However, the axial length ofthe radially outer cylindrical member 22 is shorter than that of theradially inner cylindrical member 23 and the rubber member 21. Theradially outer cylindrical member 22 is formed of a cylindrical portion22a and a bent portion 22b extending radially outward from an end of thecylindrical portion 22a near the transmission side. The surface of thebent portion 22b facing the transmission is adhered to the surface ofthe outer peripheral projection 21b facing the engine.

Each elastic portion assembly 12 is disposed in the circular aperture11c of the mass member 11, as shown in FIGS. 1, 2 and 7. The outerperipheral surface of the cylindrical portion 22a of the radially outercylindrical member 22 is fixed to the inner peripheral surface of thecircular aperture 11c. Each of the radially inner cylindrical member 23,on the other hand, is coupled to the outer peripheral portion of theinput plate 14 through a pin 16 as shown in FIG. 1. Thus, each elasticportion assembly 12 elastically couples the mass portion 11 and theinput plate 14 together in the circumferential, axial and radialdirections.

When a small amount of torque transmitted between the mass member 11 andthe input plate 14, the elasticity of the elastic portion assemblies 12in the circumferential direction primarily depends on a bending rigidityof the main portions 21a of the rubber members 21, which are diametrallyopposed to each other with the radially inner cylindrical member 23therebetween. When the torque transmitted between the mass member 11 andthe input plate 14 increases, the mass member 11 and the input plate 14move relatively to each other in the direction of rotation. Thisrelative movement causes one of the cavities 21c in each rubber member21 to collapse as shown in FIG. 12. Thereby, the elasticity of theelastic portion assembly 12 in the circumferential direction isprimarily determined by the compression rigidity of the portion of themain portion 21a of the rubber member 21. More specifically, thecompression rigidity of the portion which forms an end portion, in thecircumferential direction, of the radially inner cylindrical member 23and neighbors to the cavity 21c having the disappeared spaces. As can beseen from FIG. 12, after the spaces of one of the cavities 21c collapsesor essentially disappears, the mass portion 11 and the input plate 14are coupled substantially rigidly with substantially no elasticitytherebetween.

The axial elasticity of the elastic portion assembly 12 is primarilydetermined by the compression rigidity of the outer peripheralprojection 21b of the rubber member 21 in the axial direction as shownin FIG. 3.

The elasticity of the elastic portion assembly 12 in the radialdirection is primarily determined by the compression rigidity of themain portion 21a of the rubber member 21. More specifically, theelasticity of the elastic portion assembly 12 in the radial direction isprimarily determined by the compression rigidity of the portions of themain portion 21a which are diametrically opposed to each other with theradially inner cylindrical members 23 therebetween (see FIGS. 3 to 5).

As shown in FIGS. 1, 7 and 8, the input plate 14 is integrally formed ofan annular plate portion 14a, a conical portion 14b, a cylindricalportion 14c and a concave portion 14d. The input plate 14 is fixed atits radially inner portion to an inner race 6b of the ball bearing 6 asshown in FIG. 1, while an outer race 6a of the bearing 6 is fixed to thecrankshaft 8 of the engine as shown in FIG. 1. Accordingly, the inputplate 14 is coupled to the crankshaft 8 of the engine via the ballbearing 6 for rotational movement therebetween. However, the input plate14 is non-movably coupled to the crankshaft 8 of the engine in both theaxial and radial directions.

As shown in FIGS. 3 and 7, the annular plate portion 14a has a pluralityof apertures 14f located at its radially outer portions which restrictthe movement of the respective pins 16 in the rotating and radialdirections. As seen in FIG. 3, the annular plate portion 14a is alsoprovided with a plurality of recesses 14g for restricting the movementof heads 16a of the respective pins 16 toward the engine. Thus, movementof the elastic portion assemblies 12 toward the engine (i.e., leftwardas viewed in FIG. 3) is restricted by the heads 16a of the pins 16 whichengage recesses 14g.

The movement of the elastic portion assemblies 12 toward thetransmission is restricted by the ends of the radially inner cylindricalmembers 23 on the transmission side contacting the surface of theannular plate member 14a which faces toward the engine side. Themovement of the elastic portion assemblies 12 toward the transmission isalso restricted by the surfaces of the outer peripheral projections 21bon the transmission side contacting the surface of the annular platemember 14a facing the engine side.

The conical portion 14b extends radially inward and obliquely toward theengine from the inner periphery of the annular plate portion 14a. Theconical portion 14b is provided at its inner peripheral surface withteeth 14e (second gear) as shown in FIG. 8.

The cylindrical portion 14c extends from the inner periphery of theconical portion 14b toward the engine substantially along the axis O--O.The cylindrical portion 14c has a tapered inner peripheral surfaceconverging toward the engine.

The concave portion 14d is arranged radially inside the cylindricalportion 14c, and is provided at a center of its bottom with a recess andan aperture into which a core member 15 is inserted and fixed as notedin FIG. 1. The outer peripheral surface of the concave portion 14d isfixed to the inner race 6b of the ball bearing 6 (see FIGS. 1 and 8).

As described above, the mass portion 11 is coupled to the elasticportion assemblies 12. The elastic portion assemblies 12 are in turncoupled to the input plate 14, which is carried on the crankshaft 8 ofthe engine. Thus, these three components (the mass portion 11, theelastic portion assemblies 12 and the input plate 14) are rotatablycarried on the crankshaft 8 of the engine.

The sub-clutch 13 is a clutch mechanism of a gear-meshing type forselectively engaging and disengaging the above three components (themass member 11, the elastic portion assemblies 12 and the input plate14) with and from the input shaft 9 of the transmission. As shown inFIGS. 7-11, the sub-clutch 13 is basically formed of a synchronous gearassembly 30, a synchronous block 41, a return spring 42, a snap ring 43and the inner peripheral portions 14b, 14c and 14d of input plate 14.

As shown in FIGS. 6 and 8-11, the synchronous gear assembly 30 basicallyincludes a main body 31, a force reducing mechanism 33, a one-wayengagement member 34 and a wire ring 39. The synchronous gear assembly30 is provided with a position correcting mechanism 32, which is formedby one-way grooves 31d and one-way engagement member 34 as discussedbelow.

The main body 31 is basically formed of a large cylindrical portion 31a,a synchronous gear (first gear) 31b extending radially outward from theend of the large cylindrical portion 31a nearest to the engine, and asmall cylindrical portion 31c extending radially inward from the end ofthe large cylindrical portion 31a nearest to the engine.

The large cylindrical portion 31a is provided at its inner peripheralsurface with spline grooves 31f which are engaged with the splines ofthe input shaft 9 of the transmission (see FIG. 6). Thus, the main body31 is spline-engaged with the input shaft 9 of the transmission. Thisarrangement allows main body 31 to move axially with respect to theinput shaft 9 of the transmission. However, the main body 31 cannotrotate with respect to the input shaft 9 of the transmission. The largecylindrical portion 31a is also provided at its outer peripheral surfacewith one-way grooves 31d as shown in FIG. 6. The surfaces of eachone-way groove 31d facing the engine, i.e., the surface defining theright edge of the groove as seen in FIG. 6, is substantiallyperpendicular to the rotation axis O--O. The surface of the one-waygrooves 31d facing the transmission, i.e., the left surface as seen inFIG. 6, are inclined such that their inner peripheries are shiftedtoward the transmission with respect to their outer peripheries.

The synchronous gear 31b is opposed to the teeth 14e of the conicalportion 14b of the input plate 14. A small space is formed between theteeth 14e of the input plate 14 and the teeth of the synchronous gear31b when the sub-clutch 13 is in the disengaged state shown in FIG. 8.When the sub-clutch 13 is in the engaged state as shown in FIG. 10, theteeth 14e of input plate 14 engages the teeth of the synchronous gear31b.

The small cylindrical portion 31c of the main body 31 has a smallerdiameter than the large cylindrical portion 31a. The inner peripheralsurface of the small cylindrical portion 31c is in axially movablecontact with the core member 15. The outer peripheral surface of thesmall cylindrical portion 31c is provided with teeth at its portionnearest to the engine (left portion as viewed in FIG. 8), and is alsoprovided with an annular groove 31e at a portion nearest to thetransmission (right potion as viewed in FIG. 8). The opposite sidesurfaces of the groove 31e restrict the axial movement of the wire ring39 with respect to the main body 31. The inner peripheral surface of thegroove 31e has a diameter smaller than the inner diameter of the wirering 39 so that the wire ring 39 in the groove 31e can elastically andradially deform towards the center of the assembly.

Referring to FIGS. 1 and 6, the force reducing mechanism 33 is providedfor reducing the axial force being transmitted to the main body 31 fromthe spline hub 5c of the clutch disk assembly 5 to a predeterminedvalue. The force reducing mechanism 33 is basically formed of atransmitting member 35, a pair of springs 36, a spring retainer member37 and a ring 38, as shown in FIG. 6. The end of the transmitting member35 nearest to the transmission contacts the end surface of the splinehub 5c which faces the engine, as shown in FIG. 1.

As shown in FIG. 6, the spring retainer member 37 is formed of acylindrical inner periphery retaining portion 37a and an axialrestricting portion 37b extending radially outward from the end of theinner periphery retaining portion 37a which is nearest to the engine. Agroove 37c is formed at a portion of the outer peripheral surface of theinner periphery retaining portion 37a nearest to the transmission forholding the ring 38 therein. The springs 36 are preferably two annularconical springs. Each spring 36 has an inner diameter nearly equal tothe outer diameter of the inner periphery retaining portion 37a. Thesprings 36 are held between the end surface of the transmitting member35 nearest to the engine and the end surface of the axial restrictingportion 37b nearest to the transmission. The ring 38 is fixed in thegroove 37c and restricts the movement of the transmitting member 35toward the transmission.

The one-way engagement member 34 is an annular plate, which transmitsthe axial force between the force reducing mechanism 33 and the mainbody 31. As mentioned above, the one-way engagement member 34, togetherwith the main body 31 and the one-way grooves 31d forms the positioncorrecting mechanism 32. The inner peripheral surface of the one-wayengagement member 34 is tapered and diverges toward the engine. Theinclination of the inner peripheral surface of the one-way engagementportion 34 is substantially equal to the inclination of the surfaces ofthe one-way grooves 31d which face the transmission. The surface of theone-way engagement member 34 facing the transmission is in contact withthe axial restriction portion 37b of the spring retainer member 37 ofthe force reducing mechanism 33. The one-way engagement member 34 has apredetermined elasticity and radially deformed in an outward directionby a force applied radially outward to the inner peripheral surfacethereof.

The position correction mechanism 32 utilizes the meshing of the one-wayengagement member 34 with one of the one-way grooves 31d (i.e., a pairof one-way engagement portion) as well as elastic deformation of theone-way engagement 10 member 34 (see FIG. 6 to obtain the correctrelative position of the main body 31 and the force reducing mechanism33). This position correction mechanism 32 prevents the relativemovement in the axial direction between the force reducing mechanism 33and the main body 31 when the axial force transmitted between the forcereducing mechanism 33 and the main body 31 does not exceed apredetermined value (F1). When the axial force transmitted between theforce reducing mechanism 33 and the main body 31 exceeds thepredetermined value (F1), the position correction mechanism 32 shiftsthe main body 31 of the force reducing mechanism 33 toward the engine.When the axial force transmitted between the force reducing mechanism 33and the main body 31 is not larger than the predetermined value (F1),the force biasing the force reducing mechanism 33 toward the engine istransmitted to the main body 31 through the contact portions of theinner peripheral surface of the one-way engagement member 34 and thesurface of the one-way groove 31d opposed to the transmission. Thereby,the main body 31 moves the substantially same distance as the forcereducing mechanism 33. When the axial force transmitted between theforce reducing mechanism 33 and the main body 31 exceeds thepredetermined value (F1), a radial reaction force (F2) acts on theone-way engagement portion 34 and the main body 31 through the contactportions of the inner peripheral surface of the one-way engagementmember 34 and the surface of the one-way groove 31d opposed to thetransmission. When this force (F2) exceeds a predetermined value theforce (F2) elastically deforms the one-way engagement member 34 toincrease the inner diameter of the one-way engagement member 34 abovethe outer diameter of the surface of the one-way groove 31d. Thereby,the one-way engagement member 34 and the one-way groove 31d, whichaxially coupled the force reducing mechanism 33 and the main body 31together, are disengaged from each other, and thus the coupling betweenthe force reducing mechanism 33 and the main body 31 is temporarilyreleased so that the force reducing mechanism 33 moves toward the enginewith respect to the main body 31. Thereby, the one-way engagementportion 34 engages with the one-way groove 31d again in a new position.

Referring now to FIGS. 8-11, the wire ring 39 has a circular section anda predetermined elasticity, and is disposed in the groove 31e. The wirering 39 is designed to control the engagement between the cylindricalportion 14c of the input plate 14 and the synchronous block 41.

The synchronous block 41 has an inner peripheral surface which issplined and engages the splines of the small cylindrical portion 31c ofthe main body 31 of the synchronous gear assembly 30. Thus, synchronousblock 41 is non-rotatably and axially movably carried by the main body31. The synchronous block 41 has a conical surface 41a, which convergestoward the engine and engages wire ring 39. The conical surface 41a hasone end with a diameter larger than the outer diameter of the wire ring39 and the other end with a diameter smaller than the outer diameter ofthe wire ring 39 (see FIG. 8). The conical surface 41a contacts the wirering 39 for transmitting a force between them.

A friction member 45 is attached to the outer peripheral surface of thesynchronous block 41. The outer peripheral surface of the synchronousblock 41 and the outer surface (friction surface) of the friction member45 have the substantially same inclination as the inner peripheralsurface of the cylindrical portion 14c of the input plate 14. The outerperipheral surface of the synchronous block 41 and the outer frictionsurface of the friction member 45 are frictionally engaged with theinner peripheral surface of the cylindrical portion 14c when thesub-clutch 13 is engaged.

The return spring 42 is preferably formed of four annular conicalsprings with their inner peripheries contacting the outer peripheralsurface of the core member 15. The end of the return spring 42 nearestto the engine contacts the concave portion 14d of the input plate 14.The other end of the return spring nearest to the transmission contactsthe small cylindrical portion 31c of the main body 31 of the synchronousgear assembly 30. Thereby, the return spring 42 biases the main body 31of the synchronous gear assembly 30 toward the transmission.

The snap ring 43 has a square section, and is fitted into a grooveformed at an end of the inner peripheral surface of the cylindricalportion 14c of the input plate 14 which is nearest to the transmission.The snap ring 43 contacts the outer peripheral portion of the end of thesynchronous block 41 nearest to the transmission for restricting theaxial movement of the synchronous block 41 toward the transmission.

The operation of the coupling mechanism 1 and the dynamic damper 10 willnow be described in more detail. The rotation of the crankshaft 8 of theengine is selectively transmitted to the input shaft 9 of thetransmission through the flywheel assembly 2 and the main clutch 3. Whenthe main clutch 3 is in the disengaged state, i.e., the clutch diskassembly 5 is not frictionally engaged with the flywheel 2a and thepressure plate 4c. Also, in the disengaged state, the spline hub 5c isin the axial position shown in FIG. 1, and the sub-clutch 13 is in thedisengaged state shown in FIG. 8. When the sub-clutch 13 is in thedisengaged state shown in FIG. 8, the synchronous gear 31b is not inmesh with the teeth 14e, and the friction member 45 of the synchronousblock 41 is not in frictional engagement with the cylindrical portion14c of the input plate 14. Therefore, the synchronous gear assembly 30and the synchronous block 41 rotate together with the input shaft 9 ofthe transmission, but the input plate 14, the elastic portion assembly12 and the mass member 11 are independent of the input shaft 9 of thetransmission.

When the main clutch 3 is to be engaged, the diaphragm spring 4b forcesthe pressure plate 4c to move toward the flywheel 2a so that the clutchdisk assembly 5 is held between the flywheel 2a and the pressure plate4c. Thereby, the crankshaft 8 of the engine is coupled to the inputshaft 9 of the transmission. In this operation, as is well known, theflexible plate 2c of the flexible plate assembly 2b absorbs the axialvibration of the crankshaft 8 of the engine, and the coil springs 5b andother parts of the clutch disk assembly 5 dampen and absorb the torquevariation.

When the main clutch 3 is engaged, the spline hub 5c of the clutch diskassembly 5 moves axially toward the engine. Thereby, the spline hub 5cpushes the transmitting member 35 toward the engine to compress thesprings 36 by a predetermined length (see FIG. 9). Before the stateshown in FIG. 9 is attained, the main body 31 receives a reaction forceof the springs 36 toward the engine. However, the main body 31 hardlymoves in the axial direction because the conical surface 41a of thesynchronous block 41 restricts the axial movement of the wire ring 39.As the reaction force of the springs 36 increases, the wire ring 39elastically deforms to reduce its diameter. The elastic reaction forceof the wire ring 39 acts radially outward on the synchronous block 41 topush the same against the cylindrical portion 14c of the input plate 14.In this manner, the rotation speeds of the input shaft 9 of thetransmission and the input plate 14 are gradually synchronized with eachother owing to the friction between the friction member 45 of thesynchronous block 41 and the cylindrical portion 14c of the input plate14 until the structure attains the state shown in FIG. 9.

When the springs 36 in the state shown in FIG. 9 are further compressedto the state shown in FIG. 10, the reaction force of the springs 36 andthe amount of the elastic deformation of the wire ring 39 increase sothat the outer diameter of the deformed wire wing 39 becomes smallerthan the inner diameter of the conical surface 41a. Thereby, the wirering 39 receives from the synchronous block 41 only the force producedby the friction resistance between the wire ring 39 and the innerperipheral surface of the synchronous block 41. Since this force is muchsmaller than the reaction force of the springs 36, the springs 36 expandto move axially the main body 31 toward the engine while compressing thereturn spring 42. Thereby, the teeth of the synchronous gear 31b isengaged with the teeth 14e (see FIG. 10). In this operation, therotation of the input shaft 9 of the transmission and the rotation ofthe input plate 14 are synchronized to a certain extent so that theteeth of the synchronous gear 31b can smoothly mesh with the teeth 14e.Thereafter, the input shaft 9 of the transmission is coupled to thedynamic damper 10 through the teeth of the synchronous gear 31b and theteeth 14e meshing with each other so that a sufficient torquetransmission capacity can be achieved.

When the dynamic damper 10 is coupled to the input shaft 9 of thetransmission, the dynamic damper 10 dampens neutral noises of thetransmission and noises during driving. In particular, the dynamicdamper 10 actively dampens the vibration of the transmission in apartial rotation range.

When the coupling mechanism 1 is used for a long term, the frictionfacings 5a of the clutch disk assembly 5 of the main clutch 3 wear toreduce their axial length or thickness. This wear of the frictionfacings 5a increases the distance by which the spline hub 5c must moveaxially to engage the flywheel 12. In this case, the force reducingmechanism 33 moves further toward the engine from the position shown inFIG. 10. However, the concave portion 14d of the input plate 14 preventsthe movement of the main body 31 toward the engine through the returnspring 42 which is fully compressed so that a large reaction forceoccurs between the main body 31 and the force reducing mechanism 33.This reaction force pushes radially outward the one-way engagementmember 34 through the surface of the one-way groove 31d of the main body31 opposed to the transmission. Thereby, the one-way clutch engagementmember 34 elastically deforms to increase its diameter so that theone-way engagement member 34 is released from one of the one-way grooves31d and moves to the next one-way groove 31d. Thus, the force reducingmechanism 33 shifts toward the engine with respect to the main body 31(see FIG. 11). In this manner, the axial positional relationship betweenthe main body 31 and the force reducing mechanism 33 is corrected by theposition correction mechanism 32 in accordance with the amount of wearoccurring in the friction facings 5a. Thereby, the relative distancefrom the end of the main body 31 nearest to the transmission to the endof the transmitting member 35 nearest to the transmission changes from mas shown in FIG. 10 to n as shown in FIG. 11.

When the friction member 45 of the synchronous block 41 of thesub-clutch 13 wears, an axial component of the force by which the wirering 39 pushes the conical surface 41a of the synchronous block 41 actsto move the synchronous block 41 toward the transmission. Thereby, asshown in FIG. 11, the synchronous block 41 and the input plate 14 shiftin the axial direction relative to each other to compensate for theamount of wear occurring in the friction member 45. This axial shift isdue to the inclination of the inner peripheral surface of thecylindrical portion 14c of the input plate 14. In FIG. 11, the distanceof the above relative shifting between the synchronous block 41 and theinput plate 14 is equal to p, and the gap having a length of p formedbetween the snap ring 43 and the synchronous block 41.

When the main clutch 3 is disengaged and the spline hub 5c moves towardthe transmission, the reaction force of the return spring 42 moves therespective components of the sub-clutch 13 toward the transmission todisengaged the sub-clutch 13.

The advantages that can be achieved by employing the structure of thefirst embodiment of the present invention in the coupling mechanism 1will now be discussed.

First, the mass member 11 is radially and axially coupled to the inputplate 14 at its radially inner side by the elastic portion assemblies12. Thus, the mass member 11 is coupled to the input shaft 9 of thetransmission by the elastic portion assemblies 12 which include therubber members 21. This results in the elastic portion assemblies 12concentratedly functioning to hold and position the input portion of themass member 11 with respect to the input plate 14 in the rotating,radial and axial directions. Therefore, it is not necessary to arrangean independent support mechanism or the like. For example, anindependent support mechanism is not needed at the radially outsideportion of the mass member 11. This allows the mass member to beincreased in mass. Therefore, it is possible to increase a range inwhich damper characteristics can operate. Since each of the elasticportion assemblies 12 has an anisotropy, it is possible to setsatisfactory the elastic characteristics of the elastic portionassemblies 12 in the rotating direction to correspond to the dampercharacteristics. Moreover, it is possible to set the elasticcharacteristics of the elastic portion assemblies 12 in the radialdirection for supporting the mass member 11 without interfering withanother member.

Secondly, the dynamic damper 10 employs the rubber members 21 in theelastic portion assemblies 12. This results in the structure of theelastic portion assemblies 12 having an elasticity not only in therotating direction but also in the axial direction. Therefore, thedynamic damper 10 can operate in response to the axial vibrations fordampening the axial vibrations. The transmission has a characteristicfrequency with respect to the torsional vibration and a characteristicfrequency with respect to the axial vibration, which are different fromeach other. Therefore, the intended frequency range of the torsionalvibration to be dampened is different from the intended frequency rangeof the axial vibration to be dampened. In this connection, the rubbermembers 21 having elasticities in the rotating and axial directions isprovided with the outer peripheral projection 21b. Therefore, theelasticity of the elastic portion in the rotating direction and theelasticity of the elastic portion in the axial direction can bedetermined independently from each other, and it is possible to reduceefficiently both the kinds of vibrations, i.e., the torsional vibrationin the intended frequency range and the axial vibration in the intendedfrequency range.

Thirdly, deterioration of the rubber members 21 can be suppressed in thedynamic damper 10 of the foregoing embodiment. The dynamic damper 10receive a large torque, for example, when the main clutch 3 is engagedto start the rotation of the input shaft 9 of the transmission. Thislarge torque may apply an excessive stress to the rubber members, whichis not allowed in view of strength, and therefore, the large torque maycause deterioration of the rubber members. In this embodiment, however,the rubber members 21 are provided with the cavities 21a each having apredetermined spaces. Therefore, even if a large torque is appliedbetween the mass member 11 and the input plate 14, which is coupled tothe input shaft 9 of the transmission, the input plate 14 and the massmember 11 are substantially rigidly coupled together after the rubbermembers 21 deform to a certain extent eliminating the spaces of thecavity 21. The majority of the rubber members 21 are not subjected tothe force larger than that corresponding to the predetermineddeformation which eliminates the spaces. Accordingly, the rubber members21 employed in the dynamic damper 10 can reliably have the intendedstrength. Since the rubber members 21 between the radially outer andinner cylindrical members 22 and 23 has the cylindrical form in thisembodiment, it is possible to suppress concentration of the stress inthe rubber members 21 which may occur when it receives a force in thecircumferential direction.

Fourthly, the plurality of elastic portion assemblies 12 are employedfor coupling the input plate 14 and the mass member 11. Therefore, theportion of each elastic portion assembly 12 coupled to the input plate14 and the portion thereof coupled to the mass member 11 can be locatedat the opposite sides of each elastic portion assembly 12, in thecircumferential direction. Therefore, the force transmitted from theinput plate 14 to the mass member 11 does not act as a shearing force onthe rubber members 21, but acts as compressing and bending forces on therubber members 21. In this manner, the shearing deformation of therubber members 21 is effectively suppressed, and the bending deformationand compressing deformation, which are allowed to a larger extent thanthe shearing deformation, primarily occur in the rubber members 21.Compared with the case that the input plate 14 and the mass member 11are coupled together via the rubber members 21 deformed primarily in theshearing manner. Therefore, the stresses applied to the rubber members21, the portion coupled to the input plate 14 and the portion coupled tothe mass member 11 can be reduced without improving the quality ofmaterial of the rubber member 21 and without increasing the rigidity ofthe rubber member 21 (and thus without sacrificing a dampeningperformance).

Fifthly, the sub-clutch 13 is of the gear-meshing type which generallyallows a larger torque transmission capacity than the frictionalengagement type. Therefore, the sub-clutch 13 can have smaller sizes,and can be disposed in the radially inner portion of the couplingmechanism 1 so that increase in size of the coupling mechanism 1 issuppressed. Owing to employment of the synchronous block 41 in thesub-clutch 13, the teeth of the synchronous gear 31b can smoothly meshwith the teeth 14e of the input plate 14, and the damages to thesynchronous gear 31b and the teeth 14e of the input plate 14 can besuppressed.

Sixthly, the sub-clutch 13 has the position correcting mechanism 32.Therefore, the engaging and disengaging operations of the sub-clutch 13are not adversely affected by wearing of the friction facings 5a of themain clutch 3. Even when wear occurs in the friction facings 5a, thedynamic damper 10 can operate effectively to dampen the vibrations ofthe transmission, in the same manner as before wear of the frictionfacings 5a.

Seventhly, the ball bearing 6 in this coupling mechanism 1 has the outerrace 6a fixed to the crankshaft 8 of the engine and the inner race 6bfixed to the input plate 14 of the dynamic damper 10. Thereby, the spaceradially inside the ball bearing, which is useless in the prior art, canbe effectively utilized. More specifically, in this embodiment, thespace radially inside the ball bearing 6 is utilized for arranging thesub-clutch 13. Since the sub-clutch 13 is arranged in the radially innerportion of the coupling mechanism 1, the size of the coupling mechanism1 does not need to be increased.

According to the invention, the sub-clutch is not completely disengagedeven when the main clutch is in the disengaged state. During theoperation of engaging the main clutch, therefore, a difference betweenthe rotation speeds of the mass portion and the input shaft of thetransmission can be small so that a force applied to the components ofthe sub-clutch can be small. Accordingly, it is necessary to reduce arequired strength of the components of the sub-clutch, and the cost andsize of the sub-clutch can be reduced.

While only two embodiments have been chosen to illustrate the presentinvention, it will be apparent to those skilled in the art from thisdisclosure that various changes and modifications can be made hereinwithout departing from the scope of the invention as defined in theappended claims. Furthermore, the foregoing description of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A dynamic damper assembly adapted to be employedin a coupling mechanism including a main clutch coupled between acrankshaft of an engine and an input shaft of a transmission, andadapted to rotate with the input shaft of the transmission, said dynamicdamper assembly comprising:a mass portion adapted to rotate with theinput shaft of the transmission; a two stage sub-clutch having a firstpart coupled to said mass portion and a second part adapted to benon-rotatably coupled to the input shaft of the transmission, saidsub-clutch having a partially engaged position, in which said first andsecond parts are partially coupled together such that said mass portionrotates at a speed close to a speed of the input shaft when said mainclutch disengages the crankshaft of the engine from the input shaft ofthe transmission, and a fully engaged position, in which said first andsecond parts are fully coupled together such that said mass portion isadapted to be rotated together with the input shaft when said mainclutch engages the crankshaft of the engine to the input shaft of thetransmission; and an elastic portion operatively coupled to said massportion and adapted to elastically couple the input shaft of thetransmission and said mass portion in the rotating direction when theinput shaft of the transmission and said mass portion are interlockedtogether by said sub-clutch.
 2. The dynamic damper assembly according toclaim 1, whereinsaid sub-clutch includes a frictional engagement clutch,which remains partially engaged when the main clutch is disengaged, andwhich is fully engaged when the main clutch is engaged.
 3. The dynamicdamper assembly according to claim 1, whereinsaid sub-clutch includes agear assembly having a first gear adapted to be non-rotatably coupled tothe input shaft of the transmission and movably coupled to the inputshaft of the transmission in an axial direction, and a second gearcoupled to said mass portion.
 4. The dynamic damper assembly accordingto claim 3, whereinsaid first gear has a splined bore adapted to becoupled to the input shaft of the transmission.
 5. The dynamic damperassembly according to claim 3, whereinsaid elastic portion is arrangedbetween said mass portion and said first gear.
 6. The dynamic damperassembly according to claim 3, whereinsaid gear assembly of saidsub-clutch further includes a synchronous block non-rotatably andaxially movably coupled to said first gear, said synchronous blockhaving an outer peripheral friction surface engageable with an innerperipheral friction surface coupled to said mass portion.
 7. The dynamicdamper assembly according to claim 6, whereinsaid outer peripheralfriction surface of said synchronous block and said inner peripheralfriction surface of said mass portion are axially inclined surfaces. 8.The dynamic damper assembly according to claim 7, whereinsaidsynchronous block has a force transmitting surface with an outer conicalsection and an inner cylindrical section, and said sub-clutch furtherincludes a radially deformable ring arranged about a cylindrical portionof a main body member which is fixedly coupled to said first gear, saidsynchronous block being non-rotatably and axially movably coupled tosaid cylindrical portion of said main body member with said forcetransmitting surface engageable with said deformable ring upon axialmovement of said synchronous block on said cylindrical portion of saidmain body member.
 9. The dynamic damper assembly according to claim 8,whereinsaid sub-clutch further includes a resilient compressible memberlocated between a section of said mass portion and said main bodyportion of said first gear to normally maintain said first and secondgears in a disengaged position.
 10. The dynamic damper assemblyaccording to claim 1, whereinsaid sub-clutch further includes a couplingmember disposed between said first part and said second part, and arelease member coupled to said coupled member to move therewith forengaging and partially disengaging said first and second parts together.11. The dynamic damper assembly according to claim 10, whereinsaid firstpart includes a sub-clutch housing with said elastic portion couplingsaid mass portion to said sub-clutch housing.
 12. The dynamic damperassembly according to claim 11, whereinsaid second part is a frictionplate having an inner end non-rotatably coupled to the input shaft ofthe transmission, but movably coupled to said input shaft of thetransmission in a substantially axial direction.
 13. The dynamic damperassembly according to claim 12, whereinsaid coupling member is disposedbetween an outer end of said friction plate and a biasing member, whichbiases said coupling member to fully engage said sub-clutch housing tosaid friction plate.
 14. The dynamic damper assembly according to claim13, whereinsaid mass portion and said first part of said sub-clutch arecoupled to a bearing which is adapted to be coupled to the crankshaft ofthe engine to rotatably support said mass portion and said first part ofsaid sub-clutch on the crankshaft of the engine.
 15. A flywheel assemblyadapted to be employed in a coupling mechanism including a main clutchcoupled between a crankshaft of an engine and an input shaft of atransmission, said flywheel comprising:a flywheel adapted to benon-rotatably coupled to the crankshaft of the engine, and being adaptedto be disengageably coupled to a clutch disk assembly coupled to theinput shaft of the transmission; and a dynamic damper assembly beingadapted to be coupled to the clutch disk assembly, said dynamic damperassembly including a mass portion adapted to rotate with the input shaftof the transmission; a two stage sub-clutch having a first part coupledto said mass portion and second part adapted to be non-rotatably coupledto the input shaft of the transmission, said sub-clutch having apartially engaged position, in which said first and second parts arepartially coupled together such that said mass portion rotates at aspeed close to a speed of the input shaft when the main clutchdisengages the crankshaft of the engine from the input shaft of thetransmission, and a fully engaged position, in which said first andsecond parts are fully coupled together such that the mass portion isadapted to be rotated together with the input shaft when the main clutchengages the crankshaft of the engine to the input shaft of thetransmission; and an elastic portion operatively coupled to said massportion and adapted to elastically couple the input shaft of thetransmission and said mass portion in the rotating direction when theinput shaft of the transmission and said mass portion are interlockedtogether by said sub-clutch.
 16. The flywheel assembly according toclaim 15, further comprising:a plate member having an inner peripheralportion fixed to the crankshaft of the engine and an outer peripheralportion fixed to said flywheel, said plate member having a predeterminedrigidity to absorb vibrations along a rotation axis.
 17. The flywheelassembly according to claim 16, whereinsaid sub-clutch includes africtional engagement clutch, which remains partially engaged when themain clutch is disengaged, and which is fully engaged when the mainclutch is engaged.
 18. The flywheel assembly according to claim 16,whereinsaid sub-clutch includes a gear assembly having a first gearadapted to be non-rotatably coupled to the input shaft of thetransmission and movably coupled to the input shaft of the transmissionin an axial direction, and a second gear coupled to said mass portion.19. The flywheel assembly according to claim 18, whereinsaid first gearhas a splined bore adapted to be coupled to the input shaft of thetransmission.
 20. The flywheel assembly according to claim 18,whereinsaid elastic portion is arranged between said mass portion andsaid first gear.
 21. The flywheel assembly according to claim 18,whereinsaid gear assembly of said sub-clutch further includes asynchronous block non-rotatably and axially movably coupled to saidfirst gear, said synchronous block having an outer peripheral frictionsurface engageable with an inner peripheral friction surface coupled tosaid mass portion.
 22. The flywheel assembly according to claim 21,whereinsaid outer peripheral friction surface of said synchronous blockand said inner peripheral friction surface of said mass portion areaxially inclined surfaces.
 23. The flywheel assembly according to claim22, whereinsaid synchronous block has a force transmitting surface withan outer conical section and an inner cylindrical section, and saidsub-clutch further includes a radially deformable ring arranged about acylindrical portion of a main body member which is fixedly coupled tosaid first gear, said synchronous block being non-rotatably and axiallymovably coupled to said cylindrical portion of said main body memberwith said force transmitting surface engageable with said deformablering upon axial movement of said synchronous block on said cylindricalportion of said main body member.
 24. The flywheel assembly according toclaim 23, whereinsaid sub-clutch further includes a resilientcompressible member located between a section of said mass portion andsaid main body portion of said first gear to normally maintain saidfirst and second gears in a disengaged position.
 25. The flywheelassembly according to claim 15, whereinsaid sub-clutch further includesa coupling member disposed between said first part and said second part,and a release member coupled to said coupled member to move therewithfor engaging and partially disengaging said first and second partstogether.
 26. The flywheel assembly according to claim 25, whereinsaidfirst part includes a sub-clutch housing with said elastic portioncoupling said mass portion to said sub-clutch housing.
 27. The flywheelassembly according to claim 26, whereinsaid second part is a frictionplate having an inner en d non-rotatably coupled to the input shaft ofthe transmission, but movably coupled to said input shaft of thetransmission in a substantially axial direction.
 28. The flywheelassembly according to claim 27, whereinsaid coupling member is disposedbetween an outer end of said friction plate and a biasing member, whichbiases said coupling member to fully engage said sub-clutch housing tosaid friction plate.
 29. The flywheel assembly according to claim 28,whereinsaid mass portion and said first part of said sub-clutch arecoupled to a bearing which is adapted to be coupled to the crankshaft ofthe engine to rotatably support said mass portion and said first part ofsaid sub-clutch on the crankshaft of the engine.